1. Field of the Invention
The present invention relates to a touch panel driving apparatus and a display device including the same, and more particularly, to a touch panel driving apparatus and a display device including the same, which lead to the enhancement of sensing sensitivity.
2. Discussion of the Related Art
Recently, touch panel driving apparatuses including a touch panel are being additionally applied as input apparatuses of various multimedia devices (for example, notebook computers, portable phones, smart phones, tablet personal computers, etc.) and various display devices (for example, monitors, televisions, etc.).
Typical touch panels are categorized into capacitive touch panels, resistive touch panels, infrared touch panels, and optical touch panels. Recently, various multimedia devices including a resistive touch panel driving apparatus or a capacitive touch panel driving apparatus are being practically used.
FIG. 1 is a diagram for describing a capacitive touch panel driving apparatus of the related art.
Referring to FIG. 1, a capacitive touch panel driving apparatus of the related art includes a touch panel 10 that has a sensing capacitor Cs disposed on a transmitting line Tx and a receiving line Rx, an amplifier 20 that amplifies and outputs a sensing voltage Vsen based on the capacitance change of the sensing capacitor Cs, and a converter 30 that converts an output voltage Vo, outputted from the amplifier 20, into digital touch information DTI.
The amplifier 20 includes an inverting terminal (−) connected to the receiving line Rx, and a non-inverting terminal (+) for receiving a reference voltage signal Vref. A feedback capacitor Cf is connected between the inverting terminal (−) and output terminal (To) of the amplifier 20. The amplifier 20 amplifies the sensing voltage Vsen, based on the capacitance change of the sensing capacitor Cs, at a size rate of the feedback capacitor Cf and sensing capacitor Cs and supplies the amplified voltage to the converter 30.
The capacitive touch panel driving apparatus of the related art applies an excitation signal to the transmitting line Tx of the touch panel 10, amplifies the sensing voltage Vsen based on the capacitance change of the sensing capacitor Cs when the reference voltage signal Vref has been applied to the non-inverting terminal (+) of the amplifier 20, and converts the sensing voltage Vsen into the digital touch information DTI. Therefore, the capacitive touch panel driving apparatus of the related art detects whether the touch panel 10 is touched or a touched point, on the basis of the digital touch information DTI that is generated by touch of the touch panel 10. In this case, the output voltage Vo of the amplifier 20 is determined as expressed in Equation (1) below.
                    Vo        =                  Vref          -                                                    Cs                +                                  Δ                  ⁢                                                                          ⁢                  Cs                                            Cf                        ×            Vex                                              (        1        )            where Cs denotes an initial sensing capacitance, and ΔCs denotes a changed sensing capacitance based on a touch motion.
However, in the touch panel driving apparatus of the related art, the capacitance of the sensing capacitor Cs is less than that of a parasitic capacitor on each line formed in the touch panel 10 and moreover a changed sensing capacitance based on a touch motion is small, thereby decreasing the change of the output voltage Vo. That is, in the touch panel driving apparatus of the related art, as expressed in Equation (1), the output voltage Vo of the amplifier 20 is proportional to the changed sensing capacitance and a voltage of the excitation signal Vex. Therefore, the voltage of the excitation signal Vex is required to increase for increasing the output voltage Vo of the amplifier 20. However, when increasing the voltage of the excitation signal Vex, since a changed sensing capacitance “ΔCs” based on a touch motion is greater than an initially changed sensing capacitance, a voltage saturation occurs where the output voltage Vo of the amplifier 20 is out of the input voltage range of the converter 30.
Therefore, in the touch panel driving apparatus of the related art, the change width of the output voltage Vo of the amplifier 20 is narrow and thus sensing sensitivity is low. Due to this reason, it is difficult for the touch panel driving apparatus to determine whether the touch panel 10 is touched.